Fluxless argon arc soldering

ABSTRACT

A method of soldering wherein heat is supplied by striking an electric arc between a nonconsumable tungsten electrode and the work. The source for the arc is a bidirectional electric current. A stream of argon gas is supplied to the solder zone to shield the work for oxidation. The argon is conjunction with the bidirectional current provides a cleansing action in the solder zone permitting metallurgical bonding of the solder and work. The method is practiced without the aid of a flux.

United States Patent Inventor Appl. No.

Filed Patented Assignee FLUXLESS ARGON ARC SOLDERING 5 Claims, No Drawings U.S. Cl

823k 1/20 Field 01 Search Referencm Cited 7 Primary Examiner-J. V. Truhe Assistant Examiner.|. G. Smith Attorney-Harness, Talburtt and Baldwin ABSTRACT: A method of soldering wherein heat is supplied by striking an electric arc between a nonconsumable tungsten electrode and the work. The source for the arc is a bidirectional electric current. A stream of argon gas is sup plied to the solder zone to shield the work for oxidation. The argon is conjunction with the bidirectional current provides a cleansing action in the solder zone permitting metallurgical bonding of the solder and work. The method is practiced without the aid of a flux.

FLUXLESS ARGON ARC SOLDERING BACKGROUND I This invention is conceme'd generally with fluxless argon arc soldering of various commercial metals. However, it is particularly concerned with an improved method for the fluxless produced on welding often result in cracking of the cast iron.

To prevent these undesirable effects preheating and post heating at temperatures of 900 F. to l ,100" F. are resorted to.

SUMMARY The method of this invention eliminates the need for flux when soldering and provides true metallurgical bonds between the solder and the work. The method in its preferred form in- -volves the use of a standard inert gas (argon) arc welding unit for soldering and substitutes solder for the filler metal rod normally used in gas arc welding.

DESCRIPTION OF PREFERRED EMBODIMENT According to thisinvention, metals canbe metallurgically joined or repaired by soldering without the use of a flux by adopting the gas arc welding process to he use of solder. It is particularly beneficial in soldering or repairing cast iron and nodulariron, although it is also applicable tomost commercial metals and alloys such as copper and its alloys, aluminum and, its alloys, steel and its alloys, zinc base alloys, magnesium and its alloys, chromium. and nickel and its alloys.

ln practicing the method, an electric arc is struck between an electrode and the work. The are is used primarily to provide the necessary heat for soldering andis obtained by applying an alternating current (AC) or reverse polarity direct current (DC), both of which are hereinafter referred to collectively as "bidirectional current," to a nonconsu'mable electrode of the tungsten type. Direct current straight polarity is not suitable with this method. The bidirectional current in combination with argon causes a cleansing action in the solder zone. Simultaneous with the provision of the arc, the solder zone is flooded with welding grade argon gas. Helium is not suitable for this method. The various well-known and commercially available gas arc welding torches which have a tungsten electrode enclosed in a gas cup are most suitable for this method. To prevent rectification" of the are it is helpful to superimpose a high-frequency additional current on the heating current as is standard practice in gas arc welding.

To effect a repair or form a joint, the arc is played over the solder zone to heat the work to a teinperature suitable for melting the solder. Proper temperature has been reached when the solid solder melts as it touches the solder zone on the work. Constant 'slow movement of the'torch over the work will eliminate the possibility of localized over heating. When soldering cast or nodular iron, it is particularly important to avoid fusion of the work. Therefore, sufficient current should be applied to the electrode to melt the solder but not the work.

Following are illustrative conditions found to be satisfactory for soldering cast iron with the solder noted in Table l. Currents of 50 amps were used in the case of AC and amps were used in the case of DC reverse polarity to obtain temperatures in the neighborhood of 700800 F. on the work.

2 TABLEI Tungsten Electrode Corresponding Argon Flow Diameter Cup Size (CFH) Solder 3/32" 8 40 93% Zn-3%Al2%Cu M6" 6 40 ll I6" 6 40 Sn-40%Zn 'Linde Company Designationl Mild steel was successfully soldered with 95% Z,,5%Al solder with a resultant metallurgical bond. Nodular iron was also soldered with 93% Z,,4%Al3% Cu by this method and a metallurgical bond was obtained. The metallurgical bonds were confirmed by cross-sectioning and preparation of photomicrographs.

Table II shows several electrical currents found useful in soldering different metals.

TABLE n DC Reverse AC und Work Solder and HF. H.l-.'

.. Amps Volta Cast Iron 60%5n-4Ub2n 20 Ill 50 0.000! Mild s t-er Same 20 Ill 20 0.125" Magnesium A23! Same 20 Ill 20 0.025 Stainless 436 Sumc l5 l6 H) 0.030" Aluminum Same 20 Ill 20 0.025" /30 llrumt Same l5 l6 l0 'H.F.-supcriniposed high-frequency current as used in welding.

Having described the invention, what is claimed is:

l. A method of fluxless soldering comprising;

applying bidirectional electrical current between an electrode an an area to be soldered on a workpiece to thereby establish and maintain an electrical arc therebetween capable of heatingthe solder area to a cleaning and soldering temperature,

delivering argon gas to the area in the presence of the are to form a protective gaseous shield in the area and initiate a cleaning action in combination with the bidirectional current for the soldering operation, and

providing solder in the area in the presence of the arc and the argon and maintaining it there until itis heated to its melting point whereby soldering of the workpiece is effected.

2. The method of claim 1 wherein the workpiece to be soldered is made of iron. j

3. The method of claim 2 wherein the solder is a zinc base solder. 4. The method of polarity DC.

5. The method of claim 1 wherein the current is AC.

claim 1 wherein the current is reverse 

1. A method of fluxless soldering comprising: applying bidirectional electrical current between an electrode an an area to be soldered on a workpiece to thereby establish and maintain an electrical arc therebetween capable of heating the solder area to a cleaning and soldering temperature, delivering argon gas to the area in the presence of the arc to form a protective gaseous shield in the area and initiate a cleaning action in combination with the bidirectional current for the soldering operation, and providing solder in the area in the presence of the arc and the argon and maintaining it there until it is heated to its melting point whereby soldering of the workpiece is effected.
 2. the method of claim 1 wherein the workpiece to be soldered is made of iron.
 3. The method of claim 2 wherein the solder is a zinc base solder.
 4. The method of claim 1 wherein tHe current is reverse polarity DC.
 5. The method of claim 1 wherein the current is AC. 